Comparison of SaniPath exposure assessments in low-income urban areas in eight countries

American Society of Tropical Medicine and Hygiene 2019

November 20-24, 2019

Wolfgang Mairinger, Yuke Wang, Suraja Raj, Habib Yakubu, Casey Siesel, Jamie Green, Sarah Durry, Christine Moe

Emory University, Atlanta, GA, United States

The SaniPath exposure assessment tool compares risks of exposure to fecal contamination in urban environments across multiple exposure pathways. The tool has been deployed in 39 neighborhoods in 8 cities: Accra, Ghana, Vellore, India; Maputo, Mozambique; Siem Reap, Cambodia; Dhaka, Bangladesh; Atlanta, United States; Lusaka, Zambia; and Kampala, Uganda. Ten exposure pathways were investigated (open drains, ocean water, surface water, floodwater, public latrines, soil, bathing water, raw produce, drinking water, and street food) through behavior surveys and environmental sample analyses. Exposure was expressed as monthly dose (average amount of fecal contamination ingested as measured by E. coli colony-forming units [CFU]) and the percent of population exposed to fecal contamination for each pathway. Magnitude of fecal contamination, frequency of exposure behavior, and estimated fecal exposures were compared across pathways, neighborhoods and cities. The most common dominant exposure pathways for adults were raw produce, open drains, and street food and for children were open drains, produce, and floodwater. For produce, the dose was usually very high (>106 CFU/ month), and a large percent of the population was exposed (>80%). For street food, average E. coli concentration ranged from 101.3 CFU/serving in one neighborhood in Lusaka, Zambia to 105.5 CFU/serving in one neighborhood in Dhaka, Bangladesh. Exposure to open drains resulted in high doses (>104 CFU/month), but the population exposed varied (5%-92%) even within the same city. Exposure to fecal contamination via floodwater, usually affected a high percent of population (>80%) but had variable doses (102.5-1010 CFU/month). Both dose and percent of population exposed varied for public latrines and municipal piped water. This information can help city governments choose effective interventions to reduce the risk of exposure to fecal contamination. Widespread risks from contaminated produce and street food within and across cities underscore the link between excreta management and food safety and need for global action.

Exploring relationships of fecal exposure pathways & (a)symptomatic enteric infections in Vellore

American Society of Tropical Medicine and Hygiene 2019

November 20-24, 2019

Yuke Wang, Sydney Hubbard, Gagandeep Kang, Suraja Raj, Habib Yakubu, Arun Karthikeyan, Senthil Kumar, Venkata R. Mohan, Christine Moe

Emory University, Atlanta, GA, United States, Christian Medical College of Vellore, India, Vellore, India

Rapid urbanization has led to a sanitation crisis in many low- and middle income countries (LMIC). In March 2014, SaniPath in collaboration with the Christian Medical College (CMC) of Vellore, India conducted an exposure assessment in Old Town, a dense, urban unplanned settlement in Vellore. A total of 191 samples were collected from open drains, drinking water, public latrines, soil, raw produce, bathing water, child handrinse, and toy feeding spoon rinse and analyzed for E. coli. From March 2010 - February 2012, the MAL-ED study, a multi-site project examining enteric and growth outcomes enrolled a birth cohort of 190 children in Old Town. Multiple stool samples were collected from each child over two years of follow up and tested for bacterial and viral pathogens. Symptomatic illness was recorded. Each child in the MAL-ED study was linked with the closest environmental samples from the SaniPath study. Spatial variables, like the distance to the closest open defecation site, were generated. Generalized linear models were used with the bacterial infection rate, viral infection rate, and symptomatic illness rate as outcomes and environmental fecal contamination from different pathways and spatial variables as covariates. E. coli concentration from the closest public latrine and the distance to the closest open defecation site were significant predictors of bacterial infection rate in children. The sum of the open drain lengths within a 100-meter radius of the child, as well as the sum of street lengths within a 100-meter radius of the child, were significant predictors of viral infections in children. The E. coli concentration of the closest piped water was the only significant predictor of symptomatic illness in children. These results highlight the need for safe excreta management in dense, urban settings to prevent bacterial infections, while contaminated drinking water seems to be a major driver of symptomatic illness in this population. Human congestion, as proxied by summative surrounding street lengths and open drains, is a key risk factor for viral infection.

SaniPath_Vellore_presentation.pdf

Download PDF • 9.93MB

Risk of Exposure to Fecal Contamination in 10 Neighborhoods Across Dhaka, Bangladesh

CL Moe, J Green, S Raj, Y Wang, N Amin, S Ali, M Rahman, I Hasan, Z Hasan, S Haque, G Joseph American Society of Tropical Medicine and Hygiene Conference (October 2018)

Dhaka, Bangladesh has experienced rapid population growth and challenges meeting sanitation service demands. Poor sanitation and fecal sludge management can lead to fecal contamination in the urban environment. To understand risk of exposure to fecal contamination, an assessment of 10 environmental pathways was conducted using the SaniPath Tool. Data were collected from 10 neighborhoods (6 low-income, 2 mixed-income, and 2 high-income) throughout Dhaka between April-June 2017. 1000 environmental samples were collected from shared latrines, public play areas, produce in markets, street food, open drains, flood waters, surface waters, bathing water, municipal water, and non-municipal water. Samples were analyzed using IDEXX-Colilert-24® Quanti-Tray/2000 to determine most probable number (MPN) of E. coli. Behavior surveys were conducted with households, school children, and community groups to understand interaction with the environment. Using Bayesian methods, the behavioral and microbiological data were used to estimate the percentage of the population exposed and mean dose of fecal exposure (E. coli) for each environmental pathway in each neighbourhood. For adults, consumption of raw produce was the dominant exposure pathway (i.e. makes greatest contribution to total exposure) in 6 of the 10 neighborhoods. The percentage of adults exposed to fecal contamination through ingestion of raw produce ranged from 78-99% and the mean dose ranged from 104.8 to 107.5 MPN of E. coli ingested/month. The most common dominant pathway of exposure amongst children (8/10 neighborhoods) was accidental ingestion of drain water from playing in, or passing through, open drains (up to 94% exposed; mean dose of 107.8 MPN of E. coli ingested/month). Ingestion of fecal contamination via produce and street food was a high risk throughout Dhaka, while exposure to fecal contamination via municipal drinking water was mainly greater risk for those living in the south of the city. These results can guide city-wide WASH programming to prioritize interventions aimed at dominant exposure pathways and increase the potential for public health impact.